Acute cellular and antibody-mediated organ rejection (AMR) are constant threats for approximately 30,000 patients that receive transplants each year in the United States requiring life-long immunosuppression therapy that often comes with additional health risks. Current immunosuppressants are largely successful at thwarting acute rejection but are not overly effective at preventing AMR making it the leading cause of graft failure. Our long-term goal is to develop more effective immunosuppressants for the prevention of both acute and antibody-mediated organ rejection in transplant patients. We are investigating a promising molecular target, the kinase DNA-PK(cs), and are working to better understand how inhibiting this kinase affords potent immunosuppression in the mature activated immune system. Loss of function mutations in the PI3K kinase DNA dependent-protein kinase catalytic subunit (DNA-PK(cs)) during embryonic development in animals results in severe immunodeficiency with defects in antibody production and lymphocyte maturation. Unfortunately, the role of DNA-PK(cs) in mature activated lymphocytes remains relatively unknown. Recently we discovered that, following T cell activation, DNAPK(cs) is required for the production of critical cytokines required for a robust immune response notably both IL2 and IL6. Given this data, our laboratory investigated the ability of DNA-PK(cs) inhibitors to prevent graft rejection in a mouse skin allogenic model and discovered that loss of DNA-PK(cs) activity created an immunosuppressed environment that increased graft survival and reduced the development of donor-specific antibodies, a primary cause for AMR. We are currently working to uncover the role of DNA-PK(cs) in cytokine production and its potential as a transplant immunosuppressant through the following aims: (1) Determine the role of DNA-PK(cs) in the epigenetic regulation of cytokine expression (2) Determine the role of DNA-PK(cs) in cytokine transcription (3) Determine if DNA-PK(cs) inhibitors prevent organ rejection in a pig kidney transplant model. This data is not currently known and will provide a greater understanding of the function of DNA-PK(cs) in the immune system, its? impact on immune-related diseases and its? therapeutic potential.